Moderna Stock Declines Amidst Concerns Over RSV Vaccine Efficacy Drop

Moderna Stock

Moderna (NASDAQ:MRNA) experienced a significant dip of up to 7% on Friday following raised concerns from Wall Street analysts regarding a faster decline in the efficacy of its experimental respiratory syncytial virus (RSV) vaccine compared to rival shots from GSK (NYSE:GSK) and Pfizer (NYSE:PFE).

Data released on Thursday ahead of an RSV conference scheduled for next week indicated an efficacy of approximately 63% after 8.6 months in preventing RSV-related respiratory disease. This marks a decline from 84% efficacy observed at 3.3 months. As a result, Moderna’s shares plummeted to $89 during morning trading, following a 5.7% decrease on Thursday.

TD Cowen and UBS, prominent brokerages, expressed concerns that the vaccine’s efficacy might exhibit a steeper decline in another long-term follow-up of 14 months, potentially providing competitors with a competitive advantage. According to TD Cowen, GSK’s vaccine, Arexvy, saw a decline in efficacy to 77% at 14 months from 83%, while Pfizer’s efficacy slipped to 49% in 17 months from 67%.

Moderna cautioned against direct comparisons, citing differences in trial methodologies and case definitions for RSV disease among rival shots. Moderna emphasized the absence of head-to-head clinical trials, making it challenging to draw comparative conclusions regarding the safety and efficacy of its mRNA-1345 vaccine relative to others.

Despite these differences, TD Cowen analyst Tyler Van Buren noted concerns over the competitive profile of Moderna’s vaccine if further data confirms the trend. GSK and Pfizer had already launched their respective shots last year, and while the frequency of vaccine administration remains undecided, both companies are exploring the potential for at least two years of efficacy.

For Moderna, the RSV vaccine represents a crucial product aimed at bolstering sales as demand wanes sharply for COVID-19 shots. However, with concerns surrounding efficacy, the company faces challenges in maintaining its competitive edge in the RSV vaccine market.

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